It is a general practice in flotation of coarse ore fractions to use an extender oil to assist the attachment of such particles to bubbles. This is especially important in potash ore flotation, in which high recovery of coarse potash minerals is required. Depending on mineral grain size, potash ores are ground to either -6 mesh (3.36 mm) or -8 mesh (2.38 mm) and are classified into +20 mesh (0.85 mm) coarse and -20 mesh fine streams. In order to achieve maximum recovery of the coarse particles, these two are reagentized separately and an extender oil is added to the conditioning of the coarse stream along with a long chain primary amine. The extender oil is commonly added into the flotation pulp without pre-emulsification.
Petroleum production heavy residues are commonly used as an extender oil for the flotation of coarse potash fractions. Because of high content of polycyclic aromatic compounds such extender oils are carcinogenic and much effort has been devoted to seek low carcinogenic replacement. Dissolving amine into some oils with low content of aromatics was found to produce a good extender oil. The use of oils containing long chain amine was tested in the flotation of coarse potash fractions [J. S. Laskowski and Q. Dai, Proc. 18th Int. Mineral Processing Congress, Sydney, 1993]. Further tests have revealed that the long chain amines dissolved in the oil should be characterized by higher saturation degree (or lower iodine value).